For several years it has been recognized that containers such as cups for drinking purposes, and especially for the short term retention of hot beverages such as coffee, can be formed from various plastic materials. One very popular container material has been expanded polystyrene, both of the expanded bead, as well as foam sheet stock material.
A well known container of the above mentioned type is a one-piece cup which is molded directly from expandable polystyrene beads in a steam chest mold. However, in forming cups of the steam chest variety it is necessary, for purposes of imparting adequate strength, rigidity, liquid impermeability and surface finish, to construct such cups with what today is considered to be a thick sidewall and bottom, especially in relationship to the sidewall thickness of other types of foam sheet stock insulated cups. As a consequence of this added sidewall thickness, it is not possible to package as much product per container as can be accomplished when the sidewall is relatively thin. Thus more overall storage and shipping space is required than a comparable quantity of other types of plastic insulated cups.
Another disadvantage of the so-called steam chest molded cup is that, as an inherent consequence of its mode of manufacture, the external surface of its sidewall can only be decorated subsequent to the manufacture of the container. The necessary post decoration and printing techniques are considerably slower and more expensive than the flexographic and other sheet printing techniques which may be used to decorate sheet material prior to incorporation into containers. As a result, the majority of steam chest molded cups on the market today do not contain a decorated exterior simply because such decoration would have to be applied after the cup is fabricated.
Then too, cups have been made of insulated or expanded thermoplastic materials by cutting an arcuate blank from sheet material and forming it into a frustoconical container with techniques that are well known in the art of making paper cups. This process of cup fabrication permits the container exterior sidewall to be decorated while the plastic material is in sheet form and prior to the cutting of the arcuate sidewall blanks. By controlling the density of such sheet, it is possible to fabricate a cup with adequate strength, rigidity and liquid impermeability and which has a considerably thinner sidewall than a steam chest molded cup. Also, the ease with which the exterior of the sidewall of such cups can be provided with attractive and sometimes required decoration by predecorating the sheet from which the sidewall blanks are formed, has made it possible for a substantial number of such cups to be decorated in a way which has proven to be quite popular in the trade. One of the inherent disadvantages of such containers is the cost insofar as materials are concerned, in relationship to the steam chest molded cup, because of the scrap which is formed when crescent shaped sidewall blanks are cut from a sheet or web of stock material.
Another known type of insulated or expanded thermoplastic container which has met with some measure of commercial success is a one-piece seamless deep drawn cup which is manufactured by the well known thermoforming process. Such cups can be formed to very close manufacturing tolerances and with excellent stacking features if desired. Once again, the decoration of thermoformed deep drawn cups must be achieved subsequent to their fabrication.
As can be realized from the foregoing discussion, each of the known types of insulated containers referred to has certain advantages which make it well suited for some uses and certain limitations which make it less suited than one of the other types for other uses.
Another variation in the manufacture of cups is also known as of this time. This particular insulated cup combines a wide range of desirable properties, without offsetting limitations, and which, is well suited for a wide range of applications for insulated lightweight cups. The sidewall of such containers can be formed from rectangular blanks and, therefore, without the scrap and inherent expense involved in the severing of crescent-shaped container sidewall blanks from a sheet or web. The sidewall of such cup may be relatively inexpensively provided with attractive, high quality decorative designs. Additionally, such cup may, if desired, be provided with relatively good stacking or nesting characteristics, and with close manufacturing tolerances to provide the reliable denesting which is important in coin-operated vending machine utilization of cups. Relatively inexpensive high quality cups have been fabricated from rectangularly shaped blanks, both in a one-piece, as well as a two-piece version.
The sidewall of either a one-piece or two-piece container is formed from a web of polystyrene or other thermoplastic polymeric sheet material which has a substantial degree of orientation or heat-shrinkability built into the machine direction of the web. Decorative material is applied to the oriented web material and after printing, the web is severed into long strips, each containing the repetitive pattern of individual container blanks. The strips of material are then severed into individual container blanks which are then formed into cylindrical sleeves with the machine direction of the parent web extending circumferentially around the sleeves. In the formation of the sleeve, a liquid tight lapped seam is effected by heat or solvent sealing techniques. A sleeve winding mandrel is employed to form the sleeve to the desired diameter and to make the required side seam. The completed sleeve is then placed on a mandrel having an outer forming surface corresponding to the desired configuration of the inner surface of the container sidewall, whether such sidewall be substantially straight or tapered, such as in a nestable cup. By heating the sleeve while it is so positioned over the mandrel, the sleeve will heat shrink into conforming face to face contact with the forming surface of the mandrel. A separate bottom closure may be affixed to a sidewall formed in this manner, either while the sleeve is still in position on the mandrel, or after it is removed therefrom. Alternatively, a one-piece cup may be formed by starting with a sleeve which is highly oriented in the hoop or circumferential direction, and which exceeds the height of the forming mandrel over which it is to be telescoped by a distance of the order of from one-half to one diameter of the mandrel diametrical dimension at its smaller bottom forming end. The excess portion of the sleeve extends beyond the smaller end of the mandrel. When such a sleeve is exposed to heat, the excess portion thereof will shrink to form an annular planar portion extending inwardly across the smaller end of the mandrel and a relatively small diameter tubulation extending longitudinally from the interior of such planar portion. By the application of opposed compressive forces to such tubulation, while it is at elevated temperature, it can be caused to collapse and to fuse together to close the interior of the annular planar portion in a liquid tight fashion.
The fabrication of either a two-piece cup or a one-piece cup according to the present invention is effective to provide a cup that can be used for beverages or for the packaging of food products.
The apparatus for fabricating one-piece cups in accordance with the method of the present invention includes a drum mechanism that moves in an arcuate path and carries a plurality of spaced apart mandrels, each having an external configuration corresponding to the internal contour and configuration of the cup. The drum carries the attached mandrels through a series of operational subassemblies which function in timed sequenced interrelationship to form the container of the present invention.
With the process and apparatus of the present invention, cups having exceptional properties can be fabricated at a relatively low cost. Because the operation of the present apparatus is continuous in nature, it is extremely smooth in operation, and achieves excellent rates of container production.
It is an object of the present invention to provide an apparatus for the manufacture of cup-shaped containers.
It is an additional object of the present invention to provide a machine for the manufacture of both packing containers and beverage dispensing containers.
These and other objects have been attained in accordance with the present invention in that a machine for the manufacture of cup-shaped containers from a thermoplastic material that shrinks in a controlled fashion under the influence of heat is provided for.
It is also a feature of the present invention to provide a method and apparatus for thermally fabricating a container from a rectangular blank of oriented thermoplastic material without the need for wasting a portion of the material in such blank, and more particularly, it is a feature of the present invention to provide a method and apparatus for fabricating a container from a rectangular blank of oriented thermoplastic material wherein the rim and bottom of the container are formed substantially simultaneously.